How to open a specific tabitem on restart of WPF c# app on button click?

Question

I have multiple tabitem's (tab1, tab2, ... etc) in a WPF tabcontrol. When I click a button I want to restart the app and open a specific tabitem, say tab2 (in MVVM friendly way).

To restart the app I use

            Process.Start(Application.ResourceAssembly.Location);
            Application.Current.Shutdown();

But how do I specify which tabitem to display after restart?

Answer 1

Obiously, your new app instance needs to "know something" about the requirement to open a specific tab item.

There are other possiblities like creating a configuration file, but probably a command line parameter will serve well here. To start the new instance you may use something like Process.Start(Application.ResourceAssembly.Location, "/StartTab=MyTab3");

Then, in your ViewModel, have a string property like public string SelectedTabName {get; set;} and initialize that during the construction of the VM:

var tabInfo = Environment.GetCommandLineArgs().FirstOrDefault(a => a.ToLower().StartsWith("/starttab="));
if (!string.IsNullOrWhiteSpace(tabInfo))
{
    SelectedTabName = tabInfo.Substring(tabInfo.IndexOf('=')+1);
}

Finally, in the XAML code, bind the IsSelected property of your tab items to the SelectedTabName string, with the help of a StringToBooleanConverter, using the ConverterParameter like the name of the tab.

public class StringMatchesParameterToBooleanConverter : IValueConverter
{
    public object Convert( object value, Type targetType, object parameter, CultureInfo culture )
    {
        if (value is not string val)
            return false;

        if (parameter is not string param)
            return false;

        return val == param;
    }

    [ExcludeFromCodeCoverage]
    public object ConvertBack( object value, Type targetType, object parameter, CultureInfo culture )
    {
        throw new NotImplementedException();
    }
}

Your TabControl Xaml code could work like so

<TabControl>
    <TabControl.Resources>
        <converters:StringMatchesParameterToBooleanConverter x:Key="StringMatchesParameterToBooleanConverter" />
    </TabControl.Resources>
    <TabItem x:Name="MyTab1"
             IsSelected="{Binding SelectedTabName, Converter={StaticResource StringMatchesParameterToBooleanConverter}, ConverterParameter=MyTab1}">
    </TabItem>
    <TabItem x:Name="MyTab2"
             IsSelected="{Binding SelectedTabName, Converter={StaticResource StringMatchesParameterToBooleanConverter}, ConverterParameter=MyTab2}">
    </TabItem>
    <TabItem x:Name="MyTab3"
             IsSelected="{Binding SelectedTabName, Converter={StaticResource StringMatchesParameterToBooleanConverter}, ConverterParameter=MyTab3}">
    </TabItem>
</TabControl>